The present invention disclosed herein relates to an optical device, and more particularly, to an optical device capable of minimizing optical loss and an optical device including the same.
In general, an optical signal may be delivered along an optical waveguide or an optical fiber. Optical devices of an optical integrated circuit may be connected to an optical waveguide or an optical fiber. Additionally, the optical waveguide and the optical fiber may be connected to each other. When an optical device, an optical waveguide, and an optical fiber are connected to each other, optical loss needs to be minimized essentially during low-power and high-speed optical transmission. For example, the width and thickness of an optical waveguide for optical integrated circuit are 20 times to 450 times less than a core size of an optical fiber. Direct connection of an optical waveguide and an optical fiber may lead to high optical loss reaching about 10 dB to about 20 dB.
In order to solve the above issue, an optical coupler configured with a second waveguide having a reverse taper and overlaying waveguide with a similar refractive index to an optical fiber was suggested. The second waveguide may have advantages of low polarization or small wavelength dependence compared to a vertical incidence type grating coupler. However, when the second waveguide is coupled to a single-mode optical fiber, it requires several centimeters (cm) of a reverse taper length for low optical loss.
Because of such realistic constraints, a typical optical coupler described above may be connected to an optical fiber with a small core having a smaller core size than a single mode optical fiber. However, the optical fiber with the small core causes optical coupling efficiency to be deteriorated due to misalignment between an optical fiber and a waveguide, and also causes productivity to be lowered due to increase in optical module packaging costs.